You're talking about oxygen being in the secondary right? I gather mostly all of the 02 has left the primary after 2-4 weeks of fermenting, conditioning, and being covered with an airlock as well as a dense 2 gallons worth of C02 blanket of in his 6 gallon primary. Just wanted to clarify this for anyone who might be confused.

C02 is much heavier than Air and O2. So if you do your best to cover the carboy opening when racking, then oxygen exposure should be inconsequential for up to an hour, possibly more... and still some of that C02 will push to the secondary with the secondary opening also covered as much as it can be during racking, and more C02 created by racking on top of the dryhops. If the OP gives this 7-10 days in the secondary, I doubt he will have oxygenation issues. Even with 1 gal headspace, most of which will be taken up by the 3.5 oz. dryhops, which expand when wet.

Well regardless, if yeast carryover is what you've deemed to be the cause of haze in your glass gelatin will be a highly effective solution.

I've noticed that yeast carryover can still occur if carefully racking from primary to bottling bucket with an autosiphon. Even with an extremely high floc yeast and plenty of conditioning time. You're saying that gelatin will change that in one day? I have a hard time believing gelatin will prevent or limit yeast uptake. The yeast cake is still on the bottom of the primary either way.

What is the best way to use gelatin? I pulled up this, "I've been using gelatin for my last 12 or so batches and they all come out pretty clear. They even get clearer as time goes on. The way I do it is to use a whole tsp instead of the half that the bottle recommends, let bloom in cold water for an hour, heat to 170ish to dissolve. I then cool the solution and add it to my bottling bucket along with the priming solution."

Bob, you do have a point I always just play it safe and don't assume the there will be enough c02 in there to prevent oxidation.

I also think the other caveat with head space in secondary is you are leaving more area in there for nasties to be in there like brett, aceto, etc. It is greatly reduced if you cover the carboy. You have some solid advice there. I was just always told at my LHBS to have as little space as possible in there (secondary), but I have had a bit of headspace in secondary (probably about a gallon) and my beers turned out fine.

I guess I am just trying to say what the best practice should be, but obviously other methods totally work.

As for limiting yeast carryover, you can cold crash which will drop a good amount of yeast out. I do that and usually have a very limited amount carry over. I've never used gelatin.

By all means, correct me if I'm wrong. But leaving as little empty space as possible in the secondary would leave absolutely no room for the leaf dryhops. I've dryhopped the OP's volume in a 5 gallon secondary before and the leaf dryhops fluffed up into the neck of the carboy for a good 7 days. I assume this accounted for some of the protection. The beer tasted great. Using pellet hops would probably be the only way around leaving as little empty space as possible in the secondary yet still dryhopping big. Pellets don't take up too much space.

Even with a cold crash or gelatin, you still have a yeast cake and trub resting on the bottom of the primary, some of which (however minor or not) may still be sucked up and transferred to bottles. I think the OP's whole idea is that he wants to figure out if racking to secondary for the purposes of avoiding the cake/trub altogether is worth it for his clarity goal. It appears he knows how to cold crash and rack carefully already, yet he is still receiving 3.75 out of 5.0 in terms of clarity at best which he attributes to some minor yeast uptake. I say rack in this case. Though if it were 2.5 gallons of beer with 2 oz. dryhops, then I would not advise racking to a 5 gallon secondary.

Bob, not saying your wrong at all. With dry hopping involved I agree with your approach. It usually helps to put them in 1st and then let them hydrate as it fills up. The expansion part does present a challenge on the fill level and since hops are anti-bacterial anything that lands on them in the headspace will probably die...